Ambient light regulation methods

ABSTRACT

A lighting fixture includes a solid-state light source and control circuitry. The control circuitry is configured to receive one or more ambient light level measurements corresponding to the amount of ambient light detected by an ambient light sensor, and determine a range of values for the one or more ambient light level measurements corresponding to a desired amount of light detected by the ambient light sensor. The control circuitry is then configured to drive the solid-state light source such that the one or more ambient light level measurements received from the ambient light sensor fall within the determined range of values.

RELATED APPLICATIONS

This application is a continuation U.S. patent application Ser. No.16/578,522, filed on Sep. 23, 2019, which is a continuation of U.S.patent application Ser. No. 14/087,308, filed on Nov. 22, 2013, now U.S.Pat. No. 10,470,267, the disclosures of which are hereby incorporatedherein by reference in their entireties.

FIELD OF THE DISCLOSURE

The present disclosure relates to lighting fixtures, and in particularto monitoring ambient light with lighting fixtures and controlling thelighting fixtures accordingly.

BACKGROUND

In recent years, a movement has gained traction to replace incandescentlight bulbs with lighting fixtures that employ more efficient lightingtechnologies as well as to replace relatively efficient fluorescentlighting fixtures with lighting technologies that produce a morepleasing, natural light. One such technology that shows tremendouspromise employs solid-state lighting sources, such as light emittingdiodes (LEDs). Compared with incandescent bulbs, LED-based lightfixtures are much more efficient at converting electrical energy intolight, are longer lasting, and are also capable of producing light thatis very natural. Compared with fluorescent lighting, LED-based fixturesare also very efficient, but are capable of producing light that is muchmore natural and more capable of accurately rendering colors. As aresult, lighting fixtures that employ LED technologies are expected toreplace incandescent and fluorescent bulbs in residential, commercial,and industrial applications. As such, there is a continuing need forLED-based fixtures that can replace and at least match, and preferablyexceed, the optical performance of incandescent and fluorescent bulbs.

In lighting environments that employ LED-based fixtures, there is a needto properly illuminate the environment, and in particular, the tasksurfaces on which tasks requiring light are performed. These tasksurfaces may include workbenches, desks, conference tables, playingsurfaces, floors, walls, and the like. While lighting designers do theirbest to select the type, number, and placement of lighting fixtures forthe environment, the amount of light illuminating the task surface mayvary greatly based on the amount of ambient light that is present in theenvironment. For example, an environment with a lot of windows may havea lot of ambient sunlight during the day and little or no ambient lightin the evening. There is a need for an efficient and effective way tocompensate for the ambient light in a lighting environment.

SUMMARY

The present disclosure relates to solid-state lighting fixturesconfigured to maintain a constant amount of light on a particularsurface. According to one embodiment, a lighting fixture includes asolid-state light source and control circuitry. The control circuitry isconfigured to receive one or more ambient light level measurementscorresponding to the amount of ambient light detected by an ambientlight sensor, and determine a range of values for the one or moreambient light level measurements corresponding to a desired amount oflight detected by the ambient light sensor. The control circuitry isthen configured to drive the solid-state light source such that the oneor more ambient light level measurements received from the ambient lightsensor fall within the determined range of values.

By determining a range of values for the ambient light levelmeasurements corresponding to a desired amount of light detected by theambient light sensor rather than a single setpoint, instability withinthe control circuitry due to light detected by the ambient light sensorfrom nearby lighting fixtures is avoided.

According to one embodiment, the control circuitry of the lightingfixture is configured to receive one or more ambient light levelmeasurements corresponding to the amount of ambient light detected by anambient light sensor and determine a setpoint for the one or moreambient light level measurements corresponding with a desired amount oflight detected by the ambient light sensor. The control circuitry isthen configured to adjust the determined setpoint for the one or moreambient light level measurements based on a drive signal provided to thesolid-state light source.

By adjusting the determined setpoint for the one or more ambient lightlevel measurements based on a drive signal provided to the solid-statelight source, variations in the setpoint between lighting fixtures arereduced, thereby allowing multiple lighting fixtures in a single area toprovide a uniform amount of light.

According to one embodiment, the control circuitry of the lightingfixture is configured to receive one or more ambient light levelmeasurements corresponding to the amount of ambient light detected by anambient light sensor and determine a range of values corresponding witha desired amount of light detected by the ambient light sensor. Thecontrol circuitry is then configured to adjust the determined range ofvalues for the one or more ambient light level measurements based on adrive signal provided to the solid-state light source.

By determining a range of values for the ambient light levelmeasurements corresponding to a desired amount of light detected by theambient light sensor rather than a single setpoint, instability withinthe control circuitry due to light detected by the ambient light sensorfrom nearby lighting fixtures is avoided. Further, by adjusting thedetermined range of values for the one or more ambient light levelmeasurements based on a drive signal provided to the solid-state lightsource, variations in the range of values between lighting fixtures arereduced, thereby allowing multiple lighting fixtures in a single area toprovide a uniform amount of light.

Those skilled in the art will appreciate the scope of the disclosure andrealize additional aspects thereof after reading the following detaileddescription in association with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings incorporated in and forming a part of thisspecification illustrate several aspects of the disclosure, and togetherwith the description serve to explain the principles of the disclosure.

FIG. 1 is a perspective view of a troffer-based lighting fixtureaccording to a first embodiment of the disclosure.

FIG. 2 is a cross-section of the lighting fixture of FIG. 1.

FIG. 3 is a perspective view of a troffer-based lighting fixtureaccording to a second embodiment of the disclosure.

FIG. 4 is a cross-section of the lighting fixture of FIG. 3 according toa first embodiment.

FIG. 5 is a cross-section of the lighting fixture of FIG. 3 according toa second embodiment.

FIG. 6 illustrates a lighting environment with lighting fixtures such asthose provided in FIGS. 1 and 2.

FIG. 7 illustrates an exemplary sensor distribution beam relative to anoverall light distribution beam according to one embodiment of thedisclosure.

FIG. 8 illustrates a lighting environment with lighting fixtures such asthose provided in FIGS. 3 and 4.

FIG. 9 is a flow diagram illustrating operation of a lighting fixtureaccording to a first example.

FIG. 10 is a flow diagram illustrating operation of a lighting fixtureaccording to a second example.

FIG. 11 is a flow diagram illustrating operation of a lighting fixtureaccording to a third example.

FIGS. 12A and 12B are a communication flow diagram illustratinginteraction between two lighting fixtures according to a fourth example.

FIGS. 13A and 13B are a communication flow diagram illustratinginteraction between two lighting fixtures according to a fifth example.

FIG. 14 is a block representation of a lighting network.

FIG. 15 is a block diagram of a lighting system according to oneembodiment of the disclosure.

FIG. 16 is a flow diagram illustrating operation of a lighting fixtureaccording to a fourth example.

FIG. 17 is a flow diagram illustrating operation of a lighting fixtureaccording to a fifth example.

FIG. 18 is a flow diagram illustrating operation of a lighting fixtureaccording to a sixth example.

FIG. 19 is a cross-section of an exemplary LED according to a firstembodiment of the disclosure.

FIG. 20 is a cross-section of an exemplary LED according to a secondembodiment of the disclosure.

FIG. 21 is a schematic of a driver module and an LED array according toone embodiment of the disclosure.

FIG. 22 is a block diagram of a communications module according to oneembodiment of the disclosure.

DETAILED DESCRIPTION

The embodiments set forth below represent the necessary information toenable those skilled in the art to practice the disclosure andillustrate the best mode of practicing the disclosure. Upon reading thefollowing description in light of the accompanying drawings, thoseskilled in the art will understand the concepts of the disclosure andwill recognize applications of these concepts not particularly addressedherein. It should be understood that these concepts and applicationsfall within the scope of the disclosure and the accompanying claims.

It will be understood that relative terms such as “front,” “forward,”“rear,” “below,” “above,” “upper,” “lower,” “horizontal,” or “vertical”may be used herein to describe a relationship of one element, layer orregion to another element, layer or region as illustrated in thefigures. It will be understood that these terms are intended toencompass different orientations of the device in addition to theorientation depicted in the figures.

The present disclosure relates to lighting fixtures that can senseambient light levels and control themselves accordingly. The ambientlight in a space is generally defined as the level of light on aparticular surface, which is referred to herein as a task surface TS.Typically, lighting designers will determine a desired light level forthe one or more task surfaces TS in a space and develop a lighting planthat allocates and places a sufficient number of lighting fixtures toachieve the desired light levels on the task surfaces TS. Unfortunately,conditions in and surrounding the space significantly affect the lightlevels. For example, the color of the room or task surface TS, thepresence or lack of sunlight through adjacent windows, the reflectivenature of the task surface TS or items on the task surface TS, thepresence of uncontemplated light sources, the number of people in theroom, and the like, all influence the light levels on the task surfaceTS.

To address these issues, the present disclosure describes lightingfixtures that can accurately measure ambient light levels on a tasksurface TS and either control themselves or help control associatedlighting fixtures in a network based on the ambient light levels toprovide proper light levels on task surfaces TS. Such lighting fixturescan be implemented in various configurations, such as a troffer-typelighting fixture, recessed lighting fixture, can lights (or downlights),surface mount lighting fixtures, suspended lighting fixtures, and thelike. For purposes of illustration only, the concepts of this disclosurewill be primarily described in the context of a troffer-type lightingfixture. In general, troffer-type lighting fixtures are designed tomount in a ceiling, such as a drop ceiling of a commercial, educational,or governmental facility. Before delving into the details of ambientlight sensing, an overview of exemplary lighting fixture configurationshaving integrated ambient light sensors is provided.

In FIGS. 1 and 2, an exemplary troffer-type lighting fixture 10 is shownin isometric and cross-section views, respectively. The primarystructure of the lighting fixture 10 includes a frame 12, a light sourcehousing 14, and reflectors 16 that extend between an outer portion ofthe frame 12 and a bottom opening in the light source housing 14. A lensassembly 18 is provided over the opening of the light source housing 14.

With particular reference to FIG. 2, the illustrated light sourcehousing 14 is formed from side walls 20S, angled walls 20A, and a backwall 20B. At least the interior surface of the side walls 20S, theangled walls 20A, and the back wall 20B have reflective surfaces.Alternatively, an interior reflector structure may be provided insidethe light source housing 14. The side walls 20S extend rearward from theinside of the reflectors 16, and the angled walls 20A extend between theside walls 20S and the outer periphery of the back wall 20B. While it isnot necessary to practice the concepts disclosed herein, the back wall20B is illustrated as being substantially perpendicular to the sidewalls 20S, and the angled walls 20A form an acute angle that is lessthan 90° relative to the plane in which the lens assembly 18 lies. Thelens assembly 18 is shown as being planar and substantially parallel tothe back wall 20B; however, virtually any shape or configuration may beprovided for the lens assembly 18.

For this embodiment, an ambient light sensor S_(A) is provided outsideof the light source housing 14 and recessed in the back of a waveguide22, which has an opening 24 that resides in substantially the same planeas the lens assembly 18. The ambient light sensor S_(A) is alsoelectrically coupled to a driver module 36. Recessing the ambient lightsensor S_(A) in the back of the waveguide 22 helps prevent, or at leastreduce the amount of, light that is not reflected off of the tasksurface TS from reaching the ambient light sensor S_(A). The ambientlight sensor S_(A) may be configured to detect a broad band of visiblelight or be configured to receive or filter out select bands of thevisible and invisible light spectrum. For example, if the total amountof ambient light, including sunlight, should be detected, an ambientlight sensor S_(A) capable of detecting a broad range of light may beused. If sunlight and infrared light should not enter into the equation,the ambient light sensor S_(A) may be provided with a special coatingthat filters out red light in the visible and infrared spectrum. Detailsrelated to measuring ambient light levels and controlling the lightingfixture 10 based on the light levels are provided further below.

The back wall 20B of the light source housing 14 provides a mountingstructure for the LED array 26, which includes a mounting substrate,such as a printed circuit board (PCB), and a number of LEDs. The LEDs ofthe LED array 26 are oriented to generally emit light downward towardthe lens assembly 18. The cavity bounded by the lens assembly 18 and theinterior of the light source housing 14 provides a mixing chamber 30.Notably, the ambient light sensor S_(A) is mounted outside of the mixingchamber 30 in this embodiment, such that little or no light that exitsthe lens assembly 18 passes directly into the waveguide 22 via theopening 24. Light from the LED array 26 of the lighting fixture 10,other light sources, and the like that is reflected off of the tasksurface TS may enter the waveguide 22 and be sensed by the ambient lightsensor S_(A). Again, details related to measuring ambient light levelsand control based thereon are provided further below.

In contrast with the embodiment of FIGS. 1 and 2, FIGS. 3 and 4illustrate an embodiment wherein the ambient light sensor S_(A) islocated within the mixing chamber 30. The ambient light sensor S_(A) isconsidered to be within the mixing chamber 30 if the opening 24 of thewaveguide 22 extends to or into the mixing chamber 30. As shown in FIG.4, the ambient light sensor S_(A) is mounted on the back wall 20B of thelight source housing 14 along with the LED array 26, and is not recessedwithin a waveguide 22. FIG. 5 illustrates another embodiment where theambient light sensor S_(A) is mounted within the mixing chamber 30 andrecessed within a waveguide 22. As illustrated, the opening 24 of thewaveguide 22 is provided on the back wall 20B of the light sourcehousing 14. The waveguide 22 is substantially perpendicular to the backwall 20B. When the ambient light sensor S_(A) is provided in the mixingchamber 30, the LED array 26 may need to be turned off to achieve anaccurate measurement of ambient light, because the light in the mixingchamber 30 when the LED array 26 is on may saturate the ambient lightsensor S_(A). When the ambient light sensor S_(A) is appropriatelyconfigured and mounted outside of the mixing chamber 30, as provided inFIGS. 1 and 2, ambient light measurements may be taken when the LEDarray 26 is on.

The lens assembly 18 for any of the above embodiments may include arelatively clear lens 32 and a diffuser 34. The degree and type ofdiffusion provided by the diffuser 34 may vary from one embodiment toanother. Further, color, translucency, or opaqueness of the diffuser 34may vary from one embodiment to another. Diffusers 34, such as thatillustrated in FIG. 2, are typically formed from a polymer or glass, butother materials are viable and will be appreciated by those skilled inthe art. Similarly, the lens 32 generally corresponds to the shape andsize of the diffuser 34 as well as the front opening of the light sourcehousing 14. As with the diffuser 34, the material, color, translucency,or opaqueness of the lens 32 may vary from one embodiment to another.Further, both the diffuser 34 and the lens 32 may be formed from one ormore materials or one or more layers of the same or different materials.While only one diffuser 34 and one lens 32 are depicted, the lightingfixture 10 may have multiple diffusers 34 or lenses 32.

Light emitted from the LED array 26 is mixed inside the mixing chamber30 and directed out through the lens assembly 18. The LED array 26 mayinclude LEDs that emit different colors of light, as described furtherbelow. For example, the LED array 26 may include both red LEDs that emitred light and blue-shifted yellow (BSY) LEDs that emit bluish-yellowlight, wherein the red and bluish-yellow light is mixed to form “white”light at a desired color temperature. For a uniformly colored lightoutput, relatively thorough mixing of the light emitted from the LEDarray 26 is desired. Both the reflective interior surfaces of the lightsource housing 14 and the diffusion provided by the diffuser 34 play asignificant role in mixing the light emanated from the LED array 26.

In particular, certain light rays, which are referred to asnon-reflected light rays, emanate from the LED array 26 and exit themixing chamber 30 through the diffuser 34 and lens 32 without beingreflected off of the interior surfaces of the light source housing 14.Other light rays, which are referred to as reflected light rays, emanatefrom the LED array 26 and are reflected off of the reflective interiorsurfaces of the light source housing 14 one or more times before exitingthe mixing chamber 30 through the diffuser 34 and lens 32. With thesereflections, the reflected light rays are effectively mixed with eachother and at least some of the non-reflected light rays within themixing chamber 30 before exiting the mixing chamber 30 through thediffuser 34 and the lens 32.

As noted above, the diffuser 34 functions to diffuse, and as a resultmix, the non-reflected and reflected light rays as they exit the mixingchamber 30, wherein the mixing chamber and the diffuser 34 provide thedesired mixing of the light emanated from the LED array 26 to provide alight output of a consistent color, color temperature, or the like. Inaddition to mixing light rays, the lens 32 and diffuser 34 may beconfigured and the interior of the light source housing 14 andreflectors 16 shaped in a manner to control the relative distributionand shape of the resulting light beam, and thus the distribution oflight, that is projected from the lighting fixture 10. For example, afirst lighting fixture 10 may be designed to provide a concentratedlight output for a spotlight, wherein another may be designed to providea widely dispersed light output. From an aesthetics perspective, thediffusion provided by the diffuser 34 also prevents the emitted lightfrom looking pixelated, and obstructs the ability for a user to see theindividual LEDs of the LED array 26.

As provided in the above embodiment, the more traditional approach todiffusion is to provide a diffuser 34 that is separate from the lens 32.As such, the lens 32 is effectively transparent and does not add anyintentional diffusion.

The diffuser 34 provides the intentional diffusion. As a firstalternative, the diffuser 34 may take the form of a film that isdirectly applied to one or both surfaces of the lens 32. Such film isconsidered a “volumetric” film, wherein light diffusion occurs withinthe body of the diffusion film. One exemplary diffusion film is the ADF3030 film provided by Fusion Optix, Inc. of 19 Wheeling Avenue, WoburnMass. 01801, USA. As a second alternative, the lens assembly 18 may beconfigured as a composite lens, which provides the functionality of boththe lens 32 and the diffuser 34. Such a composite lens may be avolumetric lens, which means the light passing through the compositelens is diffused in the body of the composite lens. The composite lensreferenced above could be made of a diffusion grade acrylic or apolycarbonate material such as Bayer Makrolon®

FR7087, Makrolon® FR7067, with 0.5% to 2% diffusion doping or SabicEXRL0747-WH8F013X, EXRL0706-WHTE317X, LUX9612-WH8E490X andLUX9612-WH8E508X. The WHxxxxxx defines the degree of diffusion.

The electronics used to drive the LED array 26 are shown provided in asingle driver module 36; however, the electronics may be provided indifferent modules. Further, these electronics may be provided with wiredor wireless communications ability, as represented by the illustratedcommunications module 38. At a high level, the driver module 36 iscoupled to the LED array 26 through cabling and directly drives the LEDsof the LED array 26 based on one or a combination of internal logic;inputs received from another device, such as a switch or sensor; orcontrol information provided by the communications module 38. In theillustrated embodiment, the driver module 36 provides the primaryintelligence for the lighting fixture 10 and is capable of driving theLEDs of the LED array 26 in a desired fashion. Notably, primaryintelligence of the lighting fixture may reside in the communicationsmodule 38 in select embodiments.

The communications module 38 may act as a communication interface thatfacilitates communications between the driver module 36 and otherlighting fixtures 10, sensors (not shown), switches (not shown), aremote control system (not shown), or a portable handheld commissioningtool 40, which may also be configured to communicate with a remotecontrol system in a wired or wireless fashion. The commissioning tool 40may be used for a variety of functions, including the commissioning of alighting network or modifying the operation, configurations, settings,firmware, or software of the driver module 36 and the communicationsmodule 38. Details of an exemplary configuration that employs a drivermodule 36 and a communications module 38 are provided further below.

With reference to FIG. 6, a lighting environment is illustrated with twolighting fixtures 10. The two lighting fixtures 10 are individuallyreferenced as lighting fixture 10A and lighting fixture 10B. Thelighting fixtures 10 are in a space that includes a task surface TS,which may be subjected to sunlight during daylight hours through awindow, skylight, or the like. In this embodiment, the ambient lightsensors S_(A) are located in a waveguide 22, which is located outside ofthe mixing chamber 30.

In general, the driver module 36 will monitor the ambient light levelsthat are sensed by the ambient light sensor S_(A) and control the drivesignals that are provided to the LED array 26, based at least in part onthe detected ambient light levels. As will be described further below,the ambient light levels may be measured when the LED array 26 is on,off, or dimmed to a defined level. These one or more ambient light levelmeasurements are used to help determine how much light should be outputby the lighting fixtures 10, and thus, how the driver module 36 shoulddrive the LED array 26.

As illustrated, at least lighting fixture 10A, lighting fixture 10ft andthe sunlight coming in through an associated window project light ontothe task surface TS. These light sources may also project light ontoother room surfaces, which are not on the task surface TS or the portionof the task surface TS of interest. As such, the waveguide 22 isconfigured and the ambient light sensor S_(A) is mounted within thewaveguide 22 such that effectively only light reflected off of the tasksurface TS, or a desired portion thereof, is received by the ambientlight sensor S_(A) via the waveguide 22. In essence, the ambient lightsensor S_(A) and the waveguide 22 are configured to define a sensordistribution beam, as illustrated in FIG. 7. The sensor distributionbeam, based on where the lighting fixtures 10 are mounted, defines asensor coverage area. The sensor distribution beam may be varied basedupon the depth and diameter of the waveguide 22. As illustrated, thesensor distribution beam of FIG. 7 is more narrow than the overall lightdistribution beam afforded by the lighting fixture 10. As such, thesensor coverage area, which is defined by the sensor distribution beam,may be less in scope than the light coverage area, which is defined bythe light distribution beam. Having a narrower sensor beam distributionthan the lighting fixture's light distribution beam allows the lightingfixture 10 to have more focused ambient light sensing capabilities. Assuch, the lighting fixtures 10 may be able to detect the ambient lightlevels on the task surface TS more accurately when light reflected offof non-task surface areas is not picked up by the ambient light sensorS_(A). In other embodiments, the sensor distribution beam may be widerthan the lighting fixture's light distribution beam, or may cover thesame area as the lighting fixture's light distribution beam.

Returning to FIG. 6, one goal of lighting fixture 10A may be to adjustits light output to ensure that the portion of the task surface TS thatresides substantially immediately below the lighting fixture 10A has areference light level. Accordingly, the amount of light needed to beprovided by the lighting fixture 10A to ensure that the task surface TSis lit with the reference light level depends on not only the primarylight provided by the lighting fixture 10A, but also on the amount ofsunlight from the sun and the supplemental light provided by theadjacent lighting fixture 10B. As the amount of supplemental light andsunlight increases, the amount of primary light needed by lightingfixture 10A decreases, and vice versa.

In operation, the driver module 36 will monitor the output of theambient light sensor S_(A), and compare this output with a setpoint,which corresponds to a reference light level. The driver module 36 willadjust the primary light output by the LED array 26 until the output ofthe ambient light sensor S_(A) matches the setpoint. At this point, theportion of the task surface TS that is covered by the ambient lightsensor S_(A) for the lighting fixture 10A is being illuminated to thereference light level by the primary light output from lighting fixture10A, the supplemental light output from lighting fixture 10 ft and thesunlight. As any of these variables change, the output of the ambientlight sensor S_(A) will change, and the driver module 36 will makeadjustments to the amount of primary light output by the LED array 26 oflighting fixture 10A to ensure that the corresponding portion of thetask surface TS is illuminated with the reference light level. Processesfor determining the setpoint as well as measuring ambient light levelsare described further below.

With reference to FIG. 8, an environment similar to that illustrated inFIG. 6 is provided. In FIG. 8, the ambient light sensor S_(A) and thewaveguide 22 are provided within the mixing chamber 30 of lightingfixtures 10A and 10B. As described above, the primary light output fromlighting fixture 10A, the supplemental light output from lightingfixture 10B, and the sunlight may enter the waveguide 22, and thus bepresented to the ambient light sensor S_(A). Further, light within themixing chamber 30, which is referred to as chamber light, may bedirectly reflected off of the lens assembly 18 and into the waveguide 22with significant intensity. The intensity of the chamber light that isreflected into the waveguide 22 will likely saturate the ambient lightsensor S_(A), rendering it incapable of accurately detecting the lightintensity of the task surface TS. As will be described further below,ambient light readings using the ambient light sensor S_(A) of lightingfixture 10A will generally be taken when the LED array 26 of lightingfixture 10A is off. Ambient light sensor readings from lighting fixture10A may be shared with lighting fixture 10B, which will use thisinformation to help drive its own LED array 26. Alternatively, thedriver module 36 of lighting fixture 10A may be supplied with a look-uptable or algorithm that defines a light output level for a given ambientlight sensor output when the LED array 26 is off. In essence, lightingfixture 10A is calibrated to determine how much primary light it shouldprovide based on the light level on the task surface TS when lightingfixture 10A is off.

With reference to FIG. 9, a flow diagram illustrates one example fordetermining a setpoint and operating a lighting fixture 10 that has theambient light sensor S_(A) located outside of the mixing chamber 30,such as that illustrated in FIGS. 1, 2, and 6. The flow diagramillustrates the processing of the driver module 36 for the lightingfixture 10. Initially, the lighting fixture 10 may receive aninstruction to turn on from a lighting switch, control entity, oranother lighting fixture 10 (step 100). Before providing any drivesignals to the LED array 26, the driver module 36 may read the ambientlight sensor output, S_(A) OFF, with the LED array 26 off (step 102),and store this value.

The driver module 36 will store the ambient light sensor output and thendrive the LED array 26 at its full output (step 104) and then read theambient light sensor output, S_(A) ON, with the LED array 26 on (step106). This value is then stored. Next, the driver module 36 maydetermine a setpoint SP, by subtracting the ambient light sensor outputS_(A) OFF from the ambient light sensor output S_(A) ON (SP=S_(A)ON−S_(A) OFF) (step 108). The setpoint SP may correspond to the outputof the ambient light sensor S_(A) when the task surface TS isappropriately lit with the reference light level. This assumes that thelighting in the space in which the task surface resides is appropriatelydesigned. Alternatively, the setpoint SP may need to be manually setduring commissioning of the lighting fixture 10 and the network in whichit resides.

Once the setpoint SP is determined, the driver module 36 will monitorthe light sensor output (step 110) and drive the LED array 26, such thatthe light sensor output corresponds to the setpoint SP (step 112).Adjustment of the LED array 26 based on the light sensor output may takeplace just during initial turn on, periodically during operation,continuously during operation, or at select times as desired or definedby the designer. Further, the driver module 36 may periodically adjustthe setpoint SP. As such, the driver module 36 may determine whether toadjust the setpoint SP (step 114), and if the setpoint SP should beadjusted, determine a new setpoint SP (step 116). If the setpoint SPdoes not need to be adjusted, the process may loop back to monitoringthe light sensor output (step 110) and driving the LED array 26 suchthat the light sensor output corresponds to the setpoint SP (step 112).Similarly, once a new setpoint SP is determined (step 116), the drivermodule 36 will also monitor the light sensor output (step 110) and drivethe LED array 26 such that the light sensor output corresponds to thenew setpoint SP (step 112).

In the above process, the setpoint corresponded to the differencebetween the ambient light sensor outputs (S_(A) ON-S_(A) OFF), whichcorresponded to the LED array 26 being fully on and fully off,respectively. However, the setpoint may be determined at any two outputlevels. The flow diagram of FIG. 10 illustrates such a process.

Initially, assume that the driver module 36 is driving the LED array 26to a higher output level (OL_(Hl)), which corresponds to a higherdimming level that is less than the full output level (step 200). Atthis dimmed output level, the driver module 36 will read the ambientlight sensor output S_(A) Hl with the LED array 26 at the higher outputlevel OL_(HI) (step 202). This ambient light sensor output S_(A) Hl isstored, and then the driver module 36 will transition to driving the LEDarray 26 to a lower output level OL_(LO) (step 204). The lower outputlevel OL_(LO) corresponds to a lower dimming level than the dimminglevel associated with the higher output level OL_(Hl). The driver module36 will read the ambient light sensor output S_(A) LO with the LED array26 at the lower output level OL_(LO) (step 206), and store this value.

Next, the driver module 36 will determine the setpoint by effectivelydividing the difference in the ambient light sensor outputs (S_(A)HI-S_(A) LO) by the difference in the output levels (OL_(Hl)-OL_(LO)),wherein:

${SP} = \frac{\left( {{S_{A}HI} - {S_{A}LO}} \right)}{\left( {{OL_{HI}} - {OL}_{LO}} \right)}$

Once the setpoint is determined and stored, the driver module 36 willmonitor the light sensor output (step 210) and then drive the LED array26 such that the light sensor output corresponds to the setpoint (step212), as provided in the previous embodiment. Again, the driver module36 may determine whether or not to adjust the setpoint periodically orbased on an external input (step 214). If it is not time to adjust thesetpoint, the driver module 36 will continue to drive the LED array 26at the previous output level. If the setpoint needs to be adjusted, thedriver module 36 will determine a new setpoint as described immediatelyabove (step 216), and then continue to monitor the light output (step210) and drive the LED array 26 such that the light sensor outputcorresponds to the new setpoint (step 212).

For either of the above embodiments, changes to the output levels,whether setting to various dimming levels or simply turning on or offthe LED array 26, may take place very quickly. In fact, they may takeplace at a rate that is imperceptible to the human eye. For example, thesetpoints may be updated based on dimmed or off output levels withoutoccupants in the room noticing any change in the effective outputlevels. In essence, the light levels are modulated on and off or betweendimmed output levels at an imperceptible rate, such as at a rate greaterthan 100 cycles per second. Again, the processes associated with thepreviously described flow diagrams are generally used with embodimentswhere the ambient light sensor S_(A) is outside the mixing chamber 30.

With reference to FIG. 11, an exemplary process is illustrated foroperating a lighting fixture 10 that is configured to have the ambientlight sensor S_(A) located within the mixing chamber 30. For thisexample, assume that a look-up table or other appropriate function (suchas an algorithm) has been generated to associate a measured ambientlight sensor output with a corresponding drive level for the LED array26. For the look-up table or the algorithm, assume that the ambientlight sensor output should be read when the LED array 26 is off. Assuch, the light sensor output is read when the LED array 26 is off, andthe task surface TS is presumably illuminated to a level that is lessthan the reference light level.

Initially, the driver module 36 will receive an instruction to turn on(step 300) and then read the ambient light sensor output with the LEDarray 26 off (step 302). The ambient light sensor output is then used todetermine a drive level (step 304) by either accessing a look-up tableusing the light sensor output or determining the drive level via anappropriate algorithm based on the light sensor output. Once the drivelevel is determined, the driver module 36 will drive the LED array 26with the appropriate drive level for the given ambient light sensoroutput (step 306).

From time to time, the driver module 36 may determine that it needs torefresh the drive level (step 308). To refresh the drive level, thedriver module 36 will turn the LED array 26 off (step 310) and re-readthe ambient light sensor output with the LED array 26 off (step 312).Again, the driver module 36 will determine an updated drive level basedon the ambient light sensor output (step 314) and then drive the LEDarray 26 with the drive level corresponding to the ambient light sensoroutput (step 316). The ambient light sensor readings may take place veryquickly, wherein the driver module 36 quickly cycles the LED array 26off and then back on when the lighting fixture 10 is normally on. Aswith the illustrated process, the drive level may be set every time thelighting fixture 10 is turned on.

With the communications modules 38, the various lighting fixtures 10 ina lighting network may be able to communicate with each other to sharedata as well as control one another. For a configuration where theambient light sensor S_(A) is located within the mixing chamber 30,ambient light sensor outputs on a first lighting fixture 10 may be usedto help determine a setpoint for another lighting fixture 10. Thecommunication flow of FIGS. 12A and 12B illustrates an example whereinlighting fixture 10B determines a setpoint for lighting fixture 10A.Lighting fixtures 10A and 10B are configured in an arrangement similarto that illustrated in FIG. 8, wherein at least lighting fixture 10A hasan ambient light sensor S_(A) that is within the mixing chamber 30.

Initially, assume that lighting fixtures 10A and 10B are turned on andthe LED array 26 of each one of the lighting fixtures 10 is on (steps400 and 402). At some point, lighting fixture 10A will determine that itneeds to initially set or update its setpoint (step 404) and willsubsequently send a message that will instruct lighting fixture 10B todetermine a setpoint for lighting fixture 10A (step 406). This messagemay indicate that the LED array 26 of lighting fixture 10A is currentlyon. Lighting fixture 10B will receive the message from lighting fixture10A and will proceed to turn off its LED array 26 (step 408) and readits ambient light sensor output S_(A) HI with the LED array of lightingfixture 10A at its higher output level OL_(Hl) (step 410). Lightingfixture 10B will then turn its LED array 26 back on (step 412) and sendan instruction to lighting fixture 10A to turn its LED array 26 off(step 414). Lighting fixture 10A will respond by turning its LED array26 off (step 416) and providing a message back to lighting fixture 10Bindicating that the LED array 26 is off (or at a lower dimming level incertain embodiments) (step 418). Lighting fixture 10B will respond byturning its LED array 26 off (step 420) and reading the ambient lightsensor output S_(A) LO with the LED array 26 of lighting fixture 10A atthe lower output level OL_(LO), which is off in this particular example(step 422).

Lighting fixture 10B will then turn its LED array 26 on (step 424) andthen determine a setpoint as described above (step 426). If the ambientlight readings taken by lighting fixture 10B corresponded to lightingfixture 10A′s LED array 26 being fully on and fully off, the setpoint isdetermined by simply subtracting the respective ambient light sensoroutputs S_(A) Hl-S_(A) LO. If the respective ambient light sensoroutputs S_(A) Hl and S_(A) LO were at different dimming levels, thesetpoint is determined by dividing the difference between the ambientlight sensor outputs by the difference between the respective dimminglevels [SP=(S_(A) Hl-S_(A) LO)/(OL_(Hl)-OL_(LO))].

Once the setpoint is determined, lighting fixture 10B will send thesetpoint to lighting fixture 10A (step 428), which will store thesetpoint and turn its LED array 26 on (step 430). While lighting fixture10A currently has a setpoint, it needs an ambient light reading in orderto determine how to drive its LED array 26 to achieve the appropriatereference light level on the task surface TS. At this point, lightingfixture 10A sends a message to request an ambient light sensor readingfrom lighting fixture 10B (step 432). Lighting fixture 10B will respondby turning off its LED array 26 (step 434), reading the ambient lightsensor output (step 436), and then turning its LED array 26 back on(step 438). Lighting fixture 10B will then send the measured lightsensor output back to lighting fixture 10A (step 440), which will adjustits LED array output based on the light sensor output and the setpoint(step 442). The process of requesting ambient light sensor readings fromlighting fixture 10B may be iterative, such that lighting fixture 10Acan adjust its light output to the appropriate levels based on thesetpoint determined by lighting fixture 10B and the ambient light sensorreadings from lighting fixture 10B. Once the light output is properlyset, lighting fixture 10A may periodically request updates for theambient light sensor readings from lighting fixture 10B and adjust theoutput of the LED array 26 accordingly. Further, lighting fixture 10Amay periodically adjust the setpoint, as described above, to compensatefor changes in ambient light conditions or the reflectivity of the tasksurface TS (step 444). This may require enlisting the services oflighting fixture 10B or another lighting fixture 10.

While in the above embodiment lighting fixture 10B determines thesetpoint for lighting fixture 10A, the following embodiment has lightingfixture 10B take the ambient light sensor output readings at differentoutput levels and pass these readings to lighting fixture 10A. Lightingfixture 10A will then determine the setpoint based on the readings takenand provided by lighting fixture 10B. For this embodiment, again assumethat the ambient light sensor S_(A) is within the mixing chamber 30 ofthe respective lighting fixtures 10A and 10B.

With reference to FIGS. 13A and 13B, assume that lighting fixtures 10Aand 10B are currently on and the driver modules 36 are driving therespective LED array 26 of each one of the lighting fixtures 10 on(steps 500 and 502). At some point, lighting fixture 10A will determineit is time to update its setpoint (step 504) and will send a request forlighting fixture 10B to provide an ambient light sensor reading (step506). In response, lighting fixture 10B will turn off its LED array 26(step 508), read its ambient light sensor output (step 510), and thenturn its LED array 26 back on (step 512). Lighting fixture 10B will thensend the ambient light sensor output back to lighting fixture 10A, whichwill store the ambient light sensor output (step 516) and then turn itsLED array 26 off (step 518). Lighting fixture 10A will send anotherrequest for an ambient light sensor reading to lighting fixture 10B(step 520), which will turn off its LED array 26 (step 522), read theambient light sensor output (step 524), and then turn its LED array 26back on (step 526). Lighting fixture 10B will provide the ambient sensoroutput back to lighting fixture 10A (step 528), which will store theambient light sensor output (step 530) and then turn its LED array 26back on (step 532). Lighting fixture 10A will determine its setpoint asdescribed above (step 534) based on the respective ambient sensor outputreadings, and perhaps any available dimming levels.

At this point, lighting fixture 10A sends a message to request anambient light sensor reading from lighting fixture 10B (step 536).Lighting fixture 10B will respond by turning off its LED array 26 (step538), reading the ambient light sensor output (step 540), and thenturning its LED array 26 back on (step 542). Lighting fixture 10B willthen send the measured light sensor output back to lighting fixture 10A(step 544), which will adjust its LED array output based on the lightsensor output and the setpoint (step 546). The process of requestingambient light sensor readings from lighting fixture 10B may beiterative, such that lighting fixture 10A can adjust its light output tothe appropriate levels based on the setpoint determined by lightingfixture 10B and the ambient light sensor readings from lighting fixture10B. Once the light output is properly set, lighting fixture 10A mayperiodically request updates for the ambient light sensor readings fromlighting fixture 10B and adjust the output of the LED array 26accordingly. Further, lighting fixture 10A may periodically adjust thesetpoint, as described above, to compensate for changes in ambient lightconditions or the reflectivity of the task surface TS (step 548). Thismay require enlisting the services of lighting fixture 10B or anotherlighting fixture 10.

With reference to FIG. 14, a block representation of a lighting networkis shown with lighting fixtures 10A through 10I. Assume the lightingfixtures 10A through 10I are networked together though wirelesscommunications and form a mesh network. While a wireless mesh network isdescribed, other wired or wireless networking technologies may beemployed to facilitate communications between the various lightingfixtures 10A through 10I.

When the lighting fixtures 10A through 10I are configured such that theambient light sensor S_(A) is located outside of the mixing chamber 30,determining a setpoint and controlling how the LED array 26 of each oneof the lighting fixtures 10 are driven may take place as follows. In afirst embodiment, each of the lighting fixtures 10 determines its ownsetpoint and drives its own LED array 26 based on its own ambient sensorreadings and the setpoint. In essence, each lighting fixture 10 actssomewhat independently in this regard. The timing of the setpointprocess may take place during a power up phase, as described above inassociation with FIGS. 9 and 10. The ambient light sensor readingsneeded for the setpoint and adjusting the drive of the LED array 26 ofeach one of the lighting fixtures 10 may take place in concert or in arandomized fashion among the lighting fixtures 10A through 10I.

In a second embodiment, each lighting fixture 10 will determine its ownpreliminary setpoint and then share this setpoint with a designatedcoordinator, which could be another one of the lighting fixtures 10Athrough 10I or other device. The coordinator will process thepreliminary setpoints for all of the lighting fixtures and generate agroup setpoint. The group setpoint is then sent out to all of thelighting fixtures 10, which will use the common setpoint as describedabove to set light output levels. In more complex scenarios, thecoordinator may determine different setpoints for the different lightingfixtures 10 in the lighting network, such that different lightingfixtures 10 may function to provide different reference light levels fordifferent portions of the task surface TS or different areas in thespace. Alternatively, the preliminary setpoints of the various lightingfixtures 10 may be shared with one another, and then each lightingfixture 10 can determine a primary setpoint to use during operationbased on all or a subset of the preliminary setpoints.

Similarly, the ambient light sensor readings that are needed to generatesetpoints may be shared amongst the group, such that each lightingfixture 10 can analyze the readings from itself and the group todetermine its own setpoint. Alternatively, these readings may beprovided to the coordinator, which will determine a common setpoint forthe group or different setpoints for different lighting fixtures 10 ofthe group. Again, the measurements necessary for determining a setpointmay take place in concert as a group, in a coordinated fashion wheremeasurements are taken one lighting fixture at a time, or in anindependently randomized fashion where each lighting fixture 10 randomlyadjusts its light output in an imperceptible way and measures the outputof its ambient light sensor S_(A).

During normal operation, any one of the lighting fixtures 10 or thecoordinator may send out adjustments to the setpoint or a new setpointto all or a subset of the group to effectively raise or lower thereference light level that the lighting fixtures are trying to provideon the task surface TS. During operation, the lighting fixtures 10 mayindependently adjust their output levels to maintain the reference lightlevel based on changes in ambient room light, color, brightness,reflectivity of the task surface TS, and the like.

The same or similar operation can be provided for embodiments whereinthe ambient light sensor S_(A) is provided inside the mixing chamber 30.However, for instances where an ambient light reading must be taken fromanother lighting fixture 10, the ambient lighting readings or setpointdeterminations may be shared with numerous lighting fixtures 10 or thecoordinator for independent or group control. Any time the group needsto synchronize taking a reading or turning on or off, they can besynchronized based on time, monitoring AC line zero crossings, or atriggering message provided by one of the lighting fixtures 10. Whenrandom measurements are taken, the multiple measurements may be takenand then averaged together to effectively filter out a measurement, forexample, when multiple lighting fixtures happen to be off or on and onlyone lighting fixture should be off or on.

Turning now to FIG. 15, a block diagram of a lighting fixture 10 isprovided according to one embodiment. Assume for purposes of discussionthat the driver module 36, communications module 38, and LED array 26are ultimately connected to form the core electronics of the lightingfixture 10, and that the communications module 38 is configured tobidirectionally communicate with other lighting fixtures 10, thecommissioning tool 40, or any other entity through wired or wirelesstechniques. In this embodiment, a defined communication interface andprotocol are used to facilitate communications between the driver module36 and the communications module 38.

In the illustrated embodiment, the driver module 36 and thecommunications module 38 are coupled via a communication bus (COMM BUS)and a power bus (PWR BUS). The communication bus allows the drivermodule 36 to exchange data or commands with the communications module38. An exemplary communication bus is the well-known inter-integratedcircuitry (I²C) bus, which is a serial bus and is typically implementedwith a two-wire interface employing data and clock lines. Otheravailable buses include: serial peripheral interface (SPI) bus, DallasSemiconductor Corporation's 1-Wire serial bus, universal serial bus(USB), RS-232, Microchip Technology Incorporated's UNI/O®, and the like.

The driver module 36 may be coupled to an AC (alternating current) powersource via the AC IN port. The AC power may be controlled via a remoteswitch, wherein when an AC signal is applied, the driver module 36 willpower on and provide appropriate drive currents to the LEDs of the LEDarray 26. The AC power signal may be provided to include a desireddimming level, which is monitored by the driver module 36 and used tocontrol the drive currents to provide a light output intensitycorresponding to the dimming level. Alternatively, a separate dimmingsignal (not shown) from the AC power signal may be provided to thedriver module 36, wherein the driver module 36 will control the drivecurrents based on the dimming signal.

In this embodiment, the driver module 36 is optionally configured tocollect data from the ambient light sensor S_(A) and perhaps anoccupancy sensor S_(O) or other sensor. The driver module 36 may use thedata collected from the ambient light sensor S_(A) and the occupancysensor S_(O) to control how the LEDs of the LED array 26 are driven. Thedata collected from the ambient light sensor S_(A) and the occupancysensor S_(O) as well as any other operational parameters of the drivermodule 36 may also be shared with the communications module 38 or otherremote entities via the communications module 38.

In one or more embodiments of the present disclosure, it may bedesirable to operate the lighting fixture 10 independently, such thatthe lighting fixture 10 does not communicate with additional lightingfixtures 10 in the area. In other embodiments, it may be desirable tooperate the lighting fixture 10 at least partially independently, suchthat the lighting fixture 10 engages in limited communication withadditional lighting fixtures 10 in the area. This may be, for example,due to high network traffic in a given area, or due to other issuespreventing the networking of multiple lighting fixtures 10. Generally, asingle lighting fixture 10 may be operated independently in a given areawithout problems. However, when two or more lighting fixtures 10, suchas the lighting fixtures 10A and 10B shown in FIGS. 6 and 8, are locatedin close enough proximity to one another such that the light produced byone of the lighting fixtures, such as lighting fixture 10 ft is detectedby the ambient light sensor S_(A) of the other lighting fixture, such aslighting fixture 10A, problems may arise when each one of the lightingfixtures 10 are operated independently, as discussed in further detailbelow.

The problems described above with respect to the independent control oflighting fixtures 10 in close proximity to one another will now bediscussed as they relate to the lighting fixtures 10A and 10B shown inFIGS. 6 and 8. Because the lighting fixtures 10A and 10B are located inclose proximity to one another, the light produced by lighting fixture10A will be detected by the ambient light sensor S_(A) of lightingfixture 10 ft and the light produced by the lighting fixture 10B will bedetected by the ambient light sensor S_(A) of lighting fixture 10A.Accordingly, as lighting fixture 10A attempts to adjust the amount oflight emitted by its LED array 26 in order to reach a desired setpointdetermined for its ambient light sensor S_(A), the amount of light onthe task surface TS will change, thereby prompting lighting fixture 10Bto adjust the amount of light emitted by its LED array 26. As lightingfixture 10B then adjusts the amount of light emitted by its LED array 26in order to reach a desired setpoint determined for its ambient lightsensor S_(A), the amount of light on the task surface TS will changeagain, thereby prompting lighting fixture 10A to adjust the amount oflight emitted by its LED array 26. This cycle may continue indefinitely,causing the amount of light emitted from each one of the lightingfixtures 10 to noticeably oscillate.

FIG. 16 shows an exemplary process for independently operating alighting fixture 10 according to one embodiment of the presentdisclosure in order to avoid a visible oscillation of the light emittedfrom the lighting fixture 10 due to detection of ambient light producedby other nearby lighting fixtures 10. The described steps of the processmay illustrate one or more processing steps of the driver module 36 forthe lighting fixture 10. First, one or more ambient light levelmeasurements are received by the driver module 36, each of the one ormore ambient light level measurements corresponding to the amount ofambient light detected by (i.e., the output of) the ambient light sensorS_(A) (step 600). Next, a range of values is determined by the drivermodule 36 corresponding to a desired amount of light that should bedetected by the ambient light sensor S_(A) (step 602). Once the range ofvalues is determined, the driver module 36 then monitors the ambientlight level measurements (step 604) and drives the LED array 26 to anappropriate level, such that the one or more ambient light levelmeasurements fall within the determined range of values (step 606).

According to one embodiment, the range of values is determined by firstdetermining a setpoint for the lighting fixture 10, as described abovewith respect to both ambient light sensors S_(A) located inside andoutside of the mixing chamber 30, and subsequently determining a maximumvalue that is a fixed distance above the setpoint and a minimum valuethat is a fixed distance below the setpoint. In one embodiment, thefixed distance is 1-2% of the total signal range for the one or moreambient light level measurements. Those of ordinary skill in the artwill appreciate that the fixed distance may comprise any suitable valuewithout departing from the principles of the present disclosure.

By determining a range of values appropriate for the ambient light levelmeasurements rather than a single setpoint, lighting fixtures 10 inclose proximity to one another may be independently controlled without anoticeable oscillation of the light emitted from each one of thelighting fixtures 10. For example, when the lighting fixtures 10A and10B are independently controlled using the process shown in FIG. 16,lighting fixture 10A will attempt to adjust the amount of light emittedby its LED array 26 in order to reach a desired range of valuesdetermined for the output of its ambient light sensor S_(A). As aresult, the amount of light on the task surface TS will change, therebyprompting lighting fixture 10B to adjust the amount of light emitted byits LED array 26. As the lighting fixture 10B then adjusts the amount oflight emitted by its LED array 26, the amount of light on the tasksurface TS will change again. Although this may cause the output of theambient light sensor S_(A) of lighting fixture 10A to change slightly,the output of the ambient light sensor S_(A) will still be within therange of values determined by the driver module 36. Accordingly,lighting fixture 10A will not adjust the amount of light emitted fromits array of LEDs 26, thereby preventing oscillation of the lightingfixtures 10.

An additional problem encountered by independently controlled lightingfixtures 10 located in close proximity to one another arises when onelighting fixture 10 in an area essentially takes over most of theambient light load, causing a single lighting fixture 10 to produce adisproportionate amount of light when compared to surrounding lightingfixtures 10. Such a problem may be caused, for example, by variations inthe setpoint determined by each lighting fixture 10. If one lightingfixture 10 in an area, for example lighting fixture 10A, attempts toproduce a slightly higher light level than the other lighting fixturesdue to a higher setpoint, surrounding lighting fixtures 10, for examplelighting fixture 10 ft may compensate by producing less light. Theresult may be a noticeable difference between the light emitted byadjacent lighting fixtures 10, for example lighting fixture 10A andlighting fixture 10B.

FIG. 17 shows an exemplary process for independently operating alighting fixture 10 according to one embodiment of the presentdisclosure in order to avoid variations in the amount of light producedby lighting fixtures 10 in an area due to variations in the setpointdetermined by each one of the lighting fixtures 10. The described stepsof the process may illustrate one or more processing steps of the drivermodule 36 for the lighting fixture 10. First, one or more ambient lightlevel measurements are received by the driver module 36, each of the oneor more ambient light level measurements corresponding to the amount ofambient light detected by (i.e., the output of) the ambient light sensorS_(A) (step 700). Next, a setpoint SP is determined by the driver module36 corresponding to a desired amount of light to be detected by theambient light sensor S_(A) (step 702). The setpoint SP may be determinedas described above with respect to both ambient light sensors S_(A)located inside and outside of the mixing chamber 30. Once the setpointSP is determined, the driver module 36 then adjusts the setpoint SPbased on a drive signal provided to the LED array 26 (step 704). Thedriver module 36 then monitors the ambient light level measurements(step 706) and drives the LED array 26 to an appropriate level, suchthat the ambient light level measurements correspond to the setpoint SP(step 708). At this point, the driver module 36 may determine whetherthe drive signal has changed after the initial adjustment of thesetpoint SP (step 710). If the drive signal has changed, the setpoint SPmay be adjusted again based on the updated drive signal (step 704). Ifthe drive signal has not changed, the driver module 36 may continue tomonitor the ambient light level measurements (step 706) and drive theLED array 26 so that the ambient light level measurements correspond tothe setpoint SP (step 708).

In one exemplary embodiment, the drive signal provided to the LED array26 has an inverse relationship with the setpoint, such that an increasein the drive signal results in a decrease in the setpoint, and viceversa. Further, the setpoint may have a linear relationship with thedrive signal, or may proportionally increase or decrease based on thedrive signal.

By adjusting the setpoint based on the drive signal provided to the LEDarray 26, lighting fixtures 10 in close proximity to one another may beindependently controlled while maintaining a substantially uniformamount of light emitted from each one of the lighting fixtures 10. Forexample, when the lighting fixtures 10A and 10B are independentlycontrolled using the process shown in FIG. 17, lighting fixture 10A maydetermine a setpoint that is higher than that determined by lightingfixture 10B. Although this would normally result in a disproportionateamount of light produced by lighting fixture 10A as compared to lightingfixture 10 ft as the drive signal to the LED array 26 in lightingfixture 10A increases, the driver module 36 adjusts the setpointassociated with lighting fixture 10A downwards. Accordingly, because thedrive signal provided to the LED array 26 in lighting fixture 10A isgreater than that provided to the LED array 26 in lighting fixture 10 ftthe setpoint with each one of the lighting fixtures 10 will essentiallybalance, thereby allowing each one of the lighting fixtures 10 toproduce a substantially uniform amount of light.

In some instances, independently controlled lighting fixtures 10 mayencounter both of the previously described problems, wherein the lightemitted by adjacent lighting fixtures 10 oscillates and one lightingfixture 10 in an area essentially takes over most of the ambient lightload. FIG. 18 shows an exemplary process for independently operating alighting fixture 10 according to one embodiment of the presentdisclosure in order to avoid oscillation of the light emitted by thelighting fixture 10 as well as to avoid variations in the amount oflight emitted between lighting fixtures in an area. First, one or moreambient light level measurements are received by the driver module 36,each one of the ambient light level measurements corresponding to theamount of ambient light detect by (i.e., the output of) the ambientlight sensor S_(A) (step 800). Next, a range of values is determined bythe driver module 36 corresponding to a desired amount of light to bedetected by the ambient light sensor S_(A) (step 802). Once the range ofvalues is determined, the driver module 36 adjusts the range of valuesbased on a drive signal provided to the LED array 26 (step 804), whichmay involve adjusting the maximum value of the range of values and theminimum value of the range of values upwards or downwards based on thedrive signal. The driver module 36 then monitors the ambient light levelmeasurements (step 806) and drives the LED array 26 to an appropriatelevel, such that the ambient light level measurements fall within thedetermined range of values (step 808). At this point, the driver module36 may determine whether the drive signal has changed after the initialadjustment of the range of values (step 710). If the drive signal haschanged, the range of values may be adjusted again based on the updateddrive signal (step 804). If the drive signal has not changed, the drivermodule 36 may continue to monitor the ambient light level measurements(step 706) and drive the LED array 26 so that the ambient light levelmeasurements fall within the determined range of values (step 708).

According to one embodiment, the range of values is determined by firstdetermining a setpoint for the lighting fixture 10, as described abovewith respect to both ambient light sensors S_(A) located inside andoutside of the mixing chamber 30, and subsequently determining a maximumvalue that is a fixed distance above the setpoint and a minimum valuethat is a fixed distance below the setpoint. In one embodiment, thefixed distance is 1-2% of the total signal range for the one or moreambient light level measurements. Those of ordinary skill in the artwill appreciate that the fixed distance may comprise any suitable valuewithout departing from the principles of the present disclosure.

In one exemplary embodiment, the drive signal provided to the LED array26 has an inverse relationship with the range of values, such that anincrease in the drive signal results in a decrease in the range ofvalues, and vice versa. Further, the range of values may have a linearrelationship with the drive signal, or may proportionally increase ordecrease based on the drive signal.

By both determining a range of values appropriate for the ambient lightlevel measurements rather than a single setpoint and adjusting the rangeof values based on the drive signal provided to the LED array 26,lighting fixtures 10 in close proximity to one another may beindependently controlled without a noticeable oscillation of the lightemitted from each one of the light fixtures 10, and without a noticeabledifference in the amount of light produced between the light fixtures10, as described above.

A description of an exemplary embodiment of the LED array 26, drivermodule 36, and the communications module 38 follows. As noted, the LEDarray 26 includes a plurality of LEDs, such as the LEDs 42 illustratedin FIGS. 19 and 20. With reference to FIG. 19, a single LED chip 44 ismounted on a reflective cup 46 using solder or a conductive epoxy, suchthat ohmic contacts for the cathode (or anode) of the LED chip 44 areelectrically coupled to the bottom of the reflective cup 46. Thereflective cup 46 is either coupled to or integrally formed with a firstlead 48 of the LED 42. One or more bond wires 50 connect ohmic contactsfor the anode (or cathode) of the LED chip 44 to a second lead 52.

The reflective cup 46 may be filled with an encapsulant material 54 thatencapsulates the LED chip 44. The encapsulant material 54 may be clearor may contain a wavelength conversion material, such as a phosphor,which is described in greater detail below. The entire assembly isencapsulated in a clear protective resin 56, which may be molded in theshape of a lens to control the light emitted from the LED chip 44.

An alternative package for an LED 42 is illustrated in FIG. 20 whereinthe LED chip 44 is mounted on a substrate 58. In particular, the ohmiccontacts for the anode (or cathode) of the LED chip 44 are directlymounted to first contact pads 60 on the surface of the substrate 58. Theohmic contacts for the cathode (or anode) of the LED chip 44 areconnected to second contact pads 62, which are also on the surface ofthe substrate 58, using bond wires 64. The LED chip 44 resides in acavity of a reflector structure 66, which is formed from a reflectivematerial and functions to reflect light emitted from the LED chip 44through the opening formed by the reflector structure 66. The cavityformed by the reflector structure 66 may be filled with an encapsulantmaterial 54 that encapsulates the LED chip 44. The encapsulant material54 may be clear or may contain a wavelength conversion material, such asa phosphor.

In either of the embodiments of FIGS. 19 and 20, if the encapsulantmaterial 54 is clear, the light emitted by the LED chip 44 passesthrough the encapsulant material 54 and the protective resin 56 withoutany substantial shift in color. As such, the light emitted from the LEDchip 44 is effectively the light emitted from the LED 42. If theencapsulant material 54 contains a wavelength conversion material,substantially all or a portion of the light emitted by the LED chip 44in a first wavelength range may be absorbed by the wavelength conversionmaterial, which will responsively emit light in a second wavelengthrange. The concentration and type of wavelength conversion material willdictate how much of the light emitted by the LED chip 44 is absorbed bythe wavelength conversion material as well as the extent of thewavelength conversion. In embodiments where some of the light emitted bythe LED chip 44 passes through the wavelength conversion materialwithout being absorbed, the light passing through the wavelengthconversion material will mix with the light emitted by the wavelengthconversion material. Thus, when a wavelength conversion material isused, the light emitted from the LED 42 is shifted in color from theactual light emitted from the LED chip 44.

For example, the LED array 26 may include a group of BSY or BSG LEDs 42as well as a group of red LEDs 42. BSY LEDs 42 include an LED chip 44that emits bluish light, and the wavelength conversion material is ayellow phosphor that absorbs the blue light and emits yellowish light.Even if some of the bluish light passes through the phosphor, theresultant mix of light emitted from the overall BSY LED 42 is yellowishlight. The yellowish light emitted from a BSY LED 42 has a color pointthat falls above the Black Body Locus (BBL) on the 1931 CIE chromaticitydiagram wherein the BBL corresponds to the various color temperatures ofwhite light.

Similarly, BSG LEDs 42 include an LED chip 44 that emits bluish light;however, the wavelength conversion material is a greenish phosphor thatabsorbs the blue light and emits greenish light. Even if some of thebluish light passes through the phosphor, the resultant mix of lightemitted from the overall BSG LED 42 is greenish light. The greenishlight emitted from a BSG LED 42 has a color point that falls above theBBL on the 1931 CIE chromaticity diagram wherein the BBL corresponds tothe various color temperatures of white light.

The red LEDs 42 generally emit reddish light at a color point on theopposite side of the BBL as the yellowish or greenish light of the BSYor BSG LEDs 42. As such, the reddish light from the red LEDs 42 mixeswith the yellowish or greenish light emitted from the BSY or BSG LEDs 42to generate white light that has a desired color temperature and fallswithin a desired proximity of the BBL. In effect, the reddish light fromthe red LEDs 42 pulls the yellowish or greenish light from the BSY orBSG LEDs 42 to a desired color point on or near the BBL. Notably, thered LEDs 42 may have LED chips 44 that natively emit reddish lightwherein no wavelength conversion material is employed. Alternatively,the LED chips 44 may be associated with a wavelength conversionmaterial, wherein the resultant light emitted from the wavelengthconversion material and any light that is emitted from the LED chips 44without being absorbed by the wavelength conversion material mixes toform the desired reddish light.

The blue LED chip 44 used to form either the BSY or BSG LEDs 42 may beformed from a gallium nitride (GaN), indium gallium nitride (InGaN),silicon carbide (SiC), zinc selenide (ZnSe), or like material system.The red LED chip 44 may be formed from an aluminum indium galliumnitride (AlInGaN), gallium phosphide (GaP), aluminum gallium arsenide(AlGaAs), or like material system. Exemplary yellow phosphors includecerium-doped yttrium aluminum garnet (YAG:Ce), yellow BOSE (Ba, O, Sr,Si, Eu) phosphors, and the like. Exemplary green phosphors include greenBOSE phosphors, Lutetium aluminum garnet (LuAg), cerium doped LuAg(LuAg:Ce), Maui M535 from Lightscape Materials, Inc. of 201 WashingtonRoad, Princeton, N.J. 08540, and the like. The above LED architectures,phosphors, and material systems are merely exemplary and are notintended to provide an exhaustive listing of architectures, phosphors,and materials systems that are applicable to the concepts disclosedherein.

As noted, the LED array 26 may include a mixture of red LEDs 42 andeither BSY or BSG LEDs 42. The driver module 36 for driving the LEDarray 26 is illustrated in FIG. 21 according to one embodiment of thedisclosure. The LED array 26 may be electrically divided into two ormore strings of series connected LEDs 42. As depicted, there are threeLED strings S1, S2, and S3. For clarity, the reference number “42” willinclude a subscript indicative of the color of the LED 42 in thefollowing text where ‘R’ corresponds to red, ‘BSY’ corresponds to blueshifted yellow, ‘BSG’ corresponds to blue shifted green, and ‘BSX’corresponds to either BSG or BSY LEDs. LED string S1 includes a numberof red LEDs 42 _(R), LED string S2 includes a number of either BSY orBSG LEDs 42 _(BSX), and LED string S3 includes a number of either BSY orBSG LEDs 42_(BSX). The driver module 36 controls the current deliveredto the respective LED strings S1, S2, and S3. The current used to drivethe LEDs 42 is generally pulse width modulated (PWM), wherein the dutycycle of the pulsed current controls the intensity of the light emittedfrom the LEDs 42.

The BSY or BSG LEDs 42 _(BSX) in the second LED string S2 may beselected to have a slightly more bluish hue (less yellowish or greenishhue) than the BSY or BSG LEDs 42 _(BSX) in the third LED string S3. Assuch, the current flowing through the second and third strings S2 and S3may be tuned to control the yellowish or greenish light that iseffectively emitted by the BSY or BSG LEDs 42 _(BSX) of the second andthird LED strings S2, S3. By controlling the relative intensities of theyellowish or greenish light emitted from the differently hued BSY or BSGLEDs 42 _(BSX) of the second and third LED strings S2, S3, the hue ofthe combined yellowish or greenish light from the second and third LEDstrings S2, S3 may be controlled in a desired fashion.

The ratio of current provided through the red LEDs 42 _(R) of the firstLED string S1 relative to the currents provided through the BSY or BSGLEDs 42 _(BSX) of the second and third LED strings S2 and S3 may beadjusted to effectively control the relative intensities of the reddishlight emitted from the red LEDs 42 _(R) and the combined yellowish orgreenish light emitted from the various BSY or BSG LEDs 42 _(BSX). Assuch, the intensity and the color point of the yellowish or greenishlight from BSY or BSG LEDs 42 _(BSX) can be set relative to theintensity of the reddish light emitted from the red LEDs 42 _(R). Theresultant yellowish or greenish light mixes with the reddish light togenerate white light that has a desired color temperature and fallswithin a desired proximity of the BBL.

Notably, the number of LED strings Sx may vary from one to many anddifferent combinations of LED colors may be used in the differentstrings. The LED array 26 may have one or more strings Sx. Each LEDstring Sx may have LEDs 42 of the same color, variations of the samecolor, or substantially different colors, such as red, green, and blue.In one embodiment, a single LED string may be used for each LED array26, wherein the LEDs in the string are all substantially identical incolor, vary in substantially the same color, or include differentcolors. In another embodiment, three LED strings Sx with red, green, andblue LEDs may be used for each LED array 26, wherein each LED string Sxis dedicated to a single color. In yet another embodiment, at least twoLED strings Sx may be used, wherein different colored BSY LEDs are usedin one of the LED strings Sx and red LEDs are used in the other of theLED strings Sx.

The driver module 36 depicted in FIG. 21 generally includes rectifierand power factor correction (PFC) circuitry 68, conversion circuitry 70,and control circuitry 72. The rectifier and power factor correctioncircuitry 68 is adapted to receive an AC power signal (AC IN), rectifythe AC power signal, and correct the power factor of the AC powersignal. The resultant signal is provided to the conversion circuitry 70,which converts the rectified AC power signal to a DC power signal. TheDC power signal may be boosted or bucked to one or more desired DCvoltages by DC-DC converter circuitry, which is provided by theconversion circuitry 70. Internally, The DC power signal may be used topower the control circuitry 72 and any other circuitry provided in thedriver module 36.

The DC power signal is also provided to the power bus, which is coupledto one or more power ports, which may be part of the standardcommunication interface. The DC power signal provided to the power busmay be used to provide power to one or more external devices that arecoupled to the power bus and separate from the driver module 36. Theseexternal devices may include the communications module 38 and any numberof auxiliary devices, which are discussed further below. Accordingly,these external devices may rely on the driver module 36 for power andcan be efficiently and cost effectively designed accordingly. Therectifier and PFC circuitry 68 and the conversion circuitry 70 of thedriver module 36 are robustly designed in anticipation of being requiredto supply power to not only its internal circuitry and the LED array 26,but also to supply power to these external devices as well. Such adesign greatly simplifies the power supply design, if not eliminatingthe need for a power supply, and reduces the cost for these externaldevices.

As illustrated, the DC power signal may be provided to another port,which will be connected by cabling to the LED array 26. In thisembodiment, the supply line of the DC power signal is ultimately coupledto the first end of each of the LED strings S1, S2, and S3 in the LEDarray 26. The control circuitry 72 is coupled to the second end of eachof the LED strings S1, S2, and S3 by the cabling. Based on any number offixed or dynamic parameters, the control circuitry 72 may individuallycontrol the pulse width modulated current that flows through therespective LED strings S1, S2, and S3 such that the resultant whitelight emitted from the LED strings S1, S2, and S3 has a desired colortemperature and falls within a desired proximity of the BBL. Certain ofthe many variables that may impact the current provided to each of theLED strings S1, S2, and S3 include: the magnitude of the AC powersignal, the resultant white light, ambient temperature of the drivermodule 36 or LED array 26. Notably, the architecture used to drive theLED array 26 in this embodiment is merely exemplary, as those skilled inthe art will recognize other architectures for controlling the drivevoltages and currents presented to the LED strings S1, S2, and S3.

In certain instances, a dimming device controls the AC power signal. Therectifier and PFC circuitry 68 may be configured to detect the relativeamount of dimming associated with the AC power signal and provide acorresponding dimming signal to the control circuitry 72. Based on thedimming signal, the control circuitry 72 will adjust the currentprovided to each of the LED strings S1, S2, and S3 to effectively reducethe intensity of the resultant white light emitted from the LED stringsS1, S2, and S3 while maintaining the desired color temperature. Dimminginstructions may alternatively be delivered from the communicationsmodule 38 to the control circuitry 72 in the form of a command via thecommunication bus.

The intensity or color of the light emitted from the LEDs 42 may beaffected by ambient temperature. If associated with a thermistor S_(T)or other temperature-sensing device, the control circuitry 72 cancontrol the current provided to each of the LED strings S1, S2, and S3based on ambient temperature in an effort to compensate for adversetemperature effects. The intensity or color of the light emitted fromthe LEDs 42 may also change over time. If associated with an LED lightsensor S_(L), the control circuitry 72 can measure the color of theresultant white light being generated by the LED strings S1, S2, and S3and adjust the current provided to each of the LED strings S1, S2, andS3 to ensure that the resultant white light maintains a desired colortemperature or other desired metric. The control circuitry 72 may alsomonitor the output of the occupancy and ambient light sensors S_(O) andS_(A) for occupancy and ambient light information.

The control circuitry 72 may include a central processing unit (CPU) andsufficient memory 74 to enable the control circuitry 72 tobidirectionally communicate with the communications module 38 or otherdevices over the communication bus through an appropriate communicationinterface (I/F) 76 using a defined protocol, such as the standardprotocol described above. The control circuitry 72 may receiveinstructions from the communications module 38 or other device and takeappropriate action to implement the received instructions. Theinstructions may range from controlling how the LEDs 42 of the LED array26 are driven to returning operational data, such as temperature,occupancy, light output, or ambient light information, that wascollected by the control circuitry 72 to the communications module 38 orother device via the communication bus. The functionality of thecommunications module 38 may be integrated into the driver module 36,and vice versa.

With reference to FIG. 22, a block diagram of one embodiment of thecommunications module 38 is illustrated. The communications module 38includes a CPU 78 and associated memory 80 that contains the requisitesoftware instructions and data to facilitate operation as describedherein. The CPU 78 may be associated with a communication interface 82,which is to be coupled to the driver module 36, directly or indirectlyvia the communication bus. The CPU 78 may also be associated with awired communication port 84, a wireless communication port 86, or both,to facilitate wired or wireless communications with other lightingfixtures 10 and remote control entities.

The capabilities of the communications module 38 may vary greatly fromone embodiment to another. For example, the communications module 38 mayact as a simple bridge between the driver module 36 and the otherlighting fixtures 10 or remote control entities. In such an embodiment,the CPU 78 will primarily pass data and instructions received from theother lighting fixtures 10 or remote control entities to the drivermodule 36, and vice versa. The CPU 78 may translate the instructions asnecessary based on the protocols being used to facilitate communicationsbetween the driver module 36 and the communications module 38 as well asbetween the communications module 38 and the remote control entities. Inother embodiments, the CPU 78 plays an important role in coordinatingintelligence and sharing data among the lighting fixtures 10.

Power for the CPU 78, memory 80, the communication interface 82, and thewired and/or wireless communication ports 84 and 86 may be provided overthe power bus via the power port. As noted above, the power bus mayreceive its power from the driver module 36, which generates the DCpower signal. As such, the communications module 38 may not need to beconnected to AC power or include rectifier and conversion circuitry. Thepower port and the communication port may be separate or may beintegrated with the standard communication interface. The power port andcommunication port are shown separately for clarity. The communicationbus may take many forms. In one embodiment, the communication bus is a2-wire serial bus, wherein the connector or cabling configuration may beconfigured such that the communication bus and the power bus areprovided using four wires: data, clock, power, and ground.

Those skilled in the art will recognize improvements and modificationsto the embodiments of the present disclosure. All such improvements andmodifications are considered within the scope of the concepts disclosedherein and the claims that follow.

What is claimed is:
 1. A lighting fixture comprising: a light source;and control circuitry configured to: receive one or more ambient lightlevel measurements corresponding to an amount of ambient light detectedby an ambient light sensor; determine a setpoint for an ambient lightsensor output of the ambient light sensor based on the one or moreambient light level measurements; drive the light source according tothe setpoint; and adjust the setpoint to an adjusted setpoint based onchanges to a drive current signal provided to the light source while theambient sensor output corresponds to the setpoint.
 2. The lightingfixture of claim 1, wherein the control circuitry is further configuredto determine a first value that is below the setpoint for the ambientlight sensor output and a second value that is above the setpoint forthe ambient light sensor output.
 3. The lighting fixture of claim 2,wherein the control circuitry is further configured to adjust thesetpoint to the adjusted setpoint when changes to the drive currentsignal are detected while the ambient light sensor output falls betweenthe first value and the second value.
 4. The lighting fixture of claim1, wherein determining the setpoint for the ambient light sensor outputcomprises: reading the ambient light sensor output with the light sourcedriven at a first level to obtain one or more first ambient light levelmeasurements; reading the ambient light sensor output with the lightsource driven at a second level to obtain one or more second ambientlight level measurements; and determining the setpoint based on adifference between the one or more first ambient light levelmeasurements and the one or more second ambient light levelmeasurements.
 5. The lighting fixture of claim 4, wherein the firstlevel corresponds to the light source being driven to a fully on stateand the second level corresponds to the light source being off.
 6. Thelighting fixture of claim 4, wherein the first level corresponds to thelight source being driven at a first dimming level and the second levelcorresponds to the light source being driven at a second dimming level,which is different from the first dimming level.
 7. The lighting fixtureof claim 1, wherein the ambient light sensor is arranged outside of amixing chamber of the lighting fixture.
 8. The lighting fixture of claim1, wherein the ambient light sensor is arranged within a mixing chamberof the lighting fixture.
 9. The lighting fixture of claim 1, wherein thelight source comprises a solid-state light source.
 10. The lightingfixture of claim 1, wherein the setpoint is a group setpoint that iscommon for other lighting fixtures of a lighting fixture network. 11.The lighting fixture of claim 1, wherein the control circuitry isfurther configured to communicate adjustments to the setpoint to atleast one of another lighting fixture and a designated coordinator. 12.A lighting fixture comprising: a light source comprising a plurality oflight emitting diodes (LEDs) that are arranged in a plurality of LEDstrings; an ambient light sensor configured to provide an ambient lightsensor output; and control circuitry configured to: determine a setpointfor the ambient light sensor output based on one or more initial ambientlight level measurements, the setpoint corresponding with a lightintensity detected by the ambient light sensor; individually controleach LED string of the plurality of LED strings based on the setpoint;and adjust the setpoint to an adjusted setpoint based on changes to adrive current signal provided to at least one LED string of theplurality of LED strings while the ambient sensor output corresponds tothe setpoint.
 13. The lighting fixture of claim 12, wherein a first LEDstring of the plurality of LED strings is configured to provide light ofa same color point as light provided by a second LED string of theplurality of LED strings.
 14. The lighting fixture of claim 12, whereina first LED string of the plurality of LED strings is configured toprovide light of a different color point than light provided by a secondLED string of the plurality of LED strings.
 15. The lighting fixture ofclaim 12, wherein the plurality of LED strings are controlled by pulsewidth modulation.
 16. The lighting fixture of claim 12, wherein thecontrol circuitry is further configured to determine a first value thatis below the setpoint for the ambient light sensor output and a secondvalue that is above the setpoint for the ambient light sensor output.17. The lighting fixture of claim 16, wherein the control circuitry isfurther configured to adjust the setpoint to the adjusted setpoint whenchanges to the drive current signal are detected while the ambient lightsensor output falls between the first value and the second value. 18.The lighting fixture of claim 12, further comprising a communicationsmodule that facilitates communication between the control circuitry andan external device.
 19. The lighting fixture of claim 18, wherein theexternal device is one or more of another lighting fixture, a designatedcontroller for other lighting fixtures, a switch, a remote controlsystem, and a portable commissioning tool.
 20. The lighting fixture ofclaim 18, wherein the control circuitry is configured to bidirectionallycommunicate with the communications module.